(iii) Our quark model predicts too many states at \(E\gtrsim 1\)  GeV at \(B=0\) .
The energy splitting between the low-lying states and excited states should be bigger.
We do not fully understand how to increase the energy splitting,
but it seems to us that radial excitation energies,
related to our harmonic oscillator potential, are too small.
Within our non-relativistic model,
an ad hoc remedy would be to take a stronger harmonic oscillator potential.
But, then, we also need to substantially increase the strength of the color-electric interaction \(V_E\)  to fit low-lying spectra.
We did not attempt the parameter set leading to \(\langle V_E \rangle \lesssim -400\)  MeV,
and within such range the above-mentioned problem was not solved.
Thus we conclude that the problem is intrinsic to our model and cannot be removed by parameter choices.
Fortunately, there are relativistic versions of quark models which reproduce the hadron spectra to \(\sim 2\)  GeV quite well [1]}.
After identifying the problems in non-relativistic modeling, we now plan to proceed to the analyses using a relativistic quark model.
We leave the detailed analyses for our future work.
